The majority of large mammals, in order to reach high aerobic speed in locomotion, start running. The only exception, considering mammals with a body weight larger than 50 kg, are kangaroos, which exploit hop-ping locomotion. Experiments show that this is related to the energetic metabolic cost of the different locomotion strategies, which present advantages and disadvantages, depending on the body and muscles structure. Furthermore, recent studies illustrated that, even for humans, hopping locomotion is advantageous over running if gravity is decrease below a certain value. Experimental evidence also suggests that hopping has a lower metabolic cost than running at high locomotion speed (Fig. 1a). The objective of this work is to provide an explanation to this phenomenon utilizing a simple mechanical model, namely the so-called spring loaded inverted pendulum (SLIP) model, illustrated in Fig. 1b.
Left: Metabolic cost of quadrupedal bound compared to bipedal hop. Right: SLIP model
Objectives of the research
Provide a possible explanation of the reason why hopping locomotion is advantageous for humans only in low gravity environments, while it is always advantageous for kangaroos. Besides, explain the fact that metabolic cost in hopping decrease slower than in running for increasing locomotion speed.
1. Define a formula for evaluating the metabolic energetic cost (muscles use energy even if no me-chanical work is provided)
2. Utilizing the SLIP model, define a parameter for differentiating between running and hopping lo-comotion
3. Make numerical simulations of the model and characterize motion as type of locomotion (running or hopping) and metabolic cost
4. Variate parameters of metabolic cost function and gravitational force in order to draw conclusions about the objective of the research stated above
Proposed work strategy
Team members should divide their work according to the first three tasks, while the four tasks require the understanding and accomplishment of the first three tasks.